Rice leaf extract synthesized silver nanoparticles: An in vitro fungicidal evaluation against Rhizoctonia solani, the causative agent of sheath blight disease in rice.

Silver nanoparticles (Ag NP) were synthesized using rice leaf extract and optimized synthetic conditions were found to be 0.4 % leaf extract, 0.6 mM AgNO3 and 30 min of autoclaving. Produced NP were characterized using UV-vis, DLS, zeta potential, XRD, TEM and FTIR. Ag NP formation was established from UV-vis spectra and NP showed zeta potential value of -27.4 mV. NP were spherical, polydisperse and average size was 16.5 ± 6.2 nm. Antifungal activity of Ag NP was assessed by poisoned food technique and resazurin broth dilution against mycelium and sclerotia of fungus R. solani, the causative agent of sheath blight disease in rice. Results confirmed effective hyphal growth inhibition and % growth inhibition was dose dependent (2.5-10 μg/mL). Ag NP showed enhanced mycelial inhibition (81.7-96.7 %) at 10 μg/mL. MIC values of Ag NP were in the range of 5-10 and 15-20 μg/mL towards fungal mycelium and sclerotia, respectively. Ag NP treatment (20 μg/mL) completely inhibited the disease incidence at 20 μg/mL. Ag NP treatment (10 μg/mL) caused 1.3 and 1.5 times enhancement in seedling vigor index. Hence, Ag NP can be utilized towards management and control of various fungal diseases of crops.